The present invention relates to a high power switch and more particularly to a switch which comprises a mechanical switching element which is electromagnetically actuated and a semiconductor switching element which is turned on or off in response to an electric signal.
The contact type switch has an advantage in that it may be made compact due to a low contact resistance between contacts and a low heat generation. On the other hand, however, it has disadvantages in that it includes consumable parts such as contacts and in that an extended period of time is required for inspection and maintainance when it is used for highly repetitive opening and closing operations.
The semiconductor switch in which the flow of an electric current is controlled by a semiconductor element such as a triac causes the current to flow without involving an arc generation and contact consumption to get a long service life. However the voltage drop is remarkable when the semiconductor switch is rendered conductive. It is therefore disadvantageous in that large scale cooling fins are necessary for radiating heat and some amount of leakage current flows since the current may not be completely cut off even when non-conductive.
In these circumstances, various efforts have heretofore been made to provide the advantages of both mechanical and semiconductor switches for compensating for the disadvantages of both thereof by arranging a plurality of mechanical switches and semiconductor switches. However, the use of the different types of two switches makes the switch arrangement very expensive totally and makes the occupation space of the both switches very large. It is not easy to adopt such combined use.